A mathematical stack model of molten carbonate fuel cell was numerically solved for temperature, gas dynamic pressure, and cell performance. The model assumed a steady state, constant load operation for a co-flow stack with an external reformer. The numerical computation was done for a two-dimensional domain with a real size of cell specifications. The effect of two stack operation variables, gas utilization and system pressure, was thoroughly analysed. The computation results were demonstrated in the form of flow fields, temperature contours, axial profiles, and plots of characteristic values. Our analysis began with an underlying fact that a high cathode gas flow is necessary for stack temperature control. The analysis result verified the effect of stack cooling by the cathode gas, and showed various aspects of stack operation and performance under pressurization. The pressurization effect is most significant in a moderate pressure range of 1-5 atm. The gas dynamic pressure, as it inevitably increases at a high gas flow rate, is regulated by pressurization. All the pressurization effects can generally be represented using a dimensionless parameter, named a pressurization factor. The relation between gas dynamic pressure and total system pressure was clarified from the related flow equations. Copyright (C) 2001 John Wiley & Sons, Ltd.